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Type of star
Helium-weak stars are chemically peculiar stars which have a weak helium lines for their spectral type. Their helium lines place them in a later (i.e.
Helium-weak_star
Blue star with strong helium lines
A helium star is a class O or B star (blue), which has extraordinarily strong helium lines and weaker than normal hydrogen lines, indicating strong stellar
Helium_star
Stars with distinctly unusual metal abundances
CP1) magnetic (Ap, CP2) non-magnetic mercury-manganese (HgMn, CP3) helium-weak (He-weak, CP4). The class names provide a good idea of the peculiarities that
Chemically_peculiar_star
Variable star in the constellation Eridanus
determined that HD 28843 is a helium-weak star, based on its B-V color index being bluer (more negative) than would be expected for a star with its spectral type
HD_28843
Brief thermal runaway nuclear fusion in the core of low-mass stars
A helium flash is a very brief thermal runaway nuclear fusion of large quantities of helium into carbon through the triple-alpha process in the core of
Helium_flash
Stellar classification
main-sequence star converts the element hydrogen to helium in its core by means of nuclear fusion. The Sun is an example of a G-type main-sequence star (more
G-type_main-sequence_star
Star in the constellation Scorpius
spectroscopic and photometric study of helium weak and helium strong stars. In 1978 the star was given the variable star designation V913 Scorpii. Far more
HD_142990
Star in the Taurus constellation
peculiar star, meaning it has an unusual surface abundance of some elements as shown by its spectral lines. It is classified as a helium-weak star, but it
Maia_(star)
Low-mass supergiant that is almost devoid of hydrogen
An extreme helium star (abbreviated EHe) is a low-mass supergiant that is almost devoid of hydrogen, the most common chemical element of the Universe
Extreme_helium_star
Heterogeneous class of stars with unusual spectra
in their spectra, identified with helium, nitrogen, carbon, silicon, and oxygen, but with hydrogen lines usually weak or absent. Initially simply referred
Wolf–Rayet_star
Binary star system in constellation Cassiopeia
B5 III. It is a helium-weak star, a type of chemically peculiar star that displays abnormally weak absorption lines of helium for a star of its temperature
Omega_Cassiopeiae
Variable star in the constellation Perseus
would suggest. Such a discrepancy suggests that the star is helium-weak. The star's helium-weak nature was confirmed by William Morgan et al. in 1971
HD_21699
Stellar classification
absorption lines of ionised helium, strong lines of other ionised elements, and hydrogen and neutral helium lines weaker than spectral type B. Stars of
O-type_star
Stellar classification distinguished by bright blue luminosity
spectra showed lines of ionized helium for stars of type B0. Likewise, A0 stars also show weak lines of non-ionized helium. Subsequent catalogues of stellar
B-type_main-sequence_star
Star in the constellation Hydrus
combined with the star's rotation. It is a helium-weak star, having helium lines that are anomalously weak for its spectral type. A weak and variable longitudinal
Theta_Hydri
Alpha2 CVn variable; Corona Australis
class of B6 He wk. Si, indicating it is a helium-weak star. It has also been classified as a mercury-manganese star. V686 CrA is an α2 Canum Venaticorum variable
V686_Coronae_Australis
Star in the constellation Camelopardalis
The close pair consist of a very slowly rotating helium-weak star plus an ordinary mid-B-type star with a more rapid rotation rate. When the Hipparcos
15_Camelopardalis
absorption lines of ionised helium, strong lines of other ionised elements, and hydrogen and neutral helium lines weaker than spectral type B. This is
List_of_O-type_stars
Type of large cool star
all elements other than hydrogen and helium). These elements are all uniformly mixed throughout the star. The star "enters" the main sequence when its
Red_giant
Type of star, larger and brighter than the Sun
6. When the core helium is exhausted, a star with up to about 8 M☉ has a carbon–oxygen core that becomes degenerate and starts helium burning in a shell
Giant_star
Stellar core remnant
now host star, could be a helium planet or diamond planet. A white dwarf's stellar and planetary system is inherited from its progenitor star and may interact
White_dwarf
Large self-illuminated object in space
evolution and eventual fate. A star shines for most of its active life due to the thermonuclear fusion of hydrogen into helium in its core. This process releases
Star
Binary star in the constellation Puppis
classification is kB9 hB7 V He-w SiCrSrEuHg, indicating this is a helium-weak star. It has a magnetic field with a dipole component that is inclined 13°
HD_66051
Class of extreme chemical compounds
very weak van der Waals forces exist between helium and other atoms. This force may exceed repulsive forces, so at extremely low temperatures helium may
Helium_compounds
Star at the centre of the Solar System
a G-type main-sequence star (G2V). Every second, the Sun's core fuses about 600 billion kilograms (kg) of hydrogen into helium and converts four billion
Sun
Grouping of evolved cool luminous stars
approximately 3×108 K, helium burning (fusion of helium nuclei) begins. The onset of helium burning in the core halts the star's cooling and increase in
Asymptotic_giant_branch
Star in the constellation Centaurus
was confirmed by A. D. Thackeray in 1966. The star ranges from a helium-strong B2 class to a helium-weak B8 with a period of 8.82 days. Radial velocity
HD_125823
Changes to stars over their lifespans
atoms at the core of the main-sequence star. Later, as the preponderance of atoms at the core becomes helium, stars like the Sun begin to fuse hydrogen
Stellar_evolution
Creation of chemical elements within stars
their lifespans, first by burning hydrogen (main sequence star), then helium (horizontal branch star), and progressively burning higher elements. However,
Stellar_nucleosynthesis
Star whose atmosphere contains more carbon than oxygen
so that the helium fusion ceases, and the hydrogen shell burning restarts. During these shell helium flashes, the mass loss from the star is significant
Carbon_star
Star in the constellation Puppis
a strong magnetic field. It is classified as a He-weak star and in addition to a deficit of helium in its spectrum, it shows an overabundance of many
K_Puppis
Classification of stars based on spectral properties
DB – a helium-rich atmosphere, indicated by neutral helium, He I, spectral lines. DO – a helium-rich atmosphere, indicated by ionized helium, He II,
Stellar_classification
Type of cataclysmic variable star
companion star. These binaries have extremely short orbital periods (shorter than about one hour) and have unusual spectra dominated by helium with hydrogen
AM_Canum_Venaticorum_star
Continuous band of stars that appears on plots of stellar color versus brightness
generally refer to the metallicity of the star. This is the abundance of heavier-than-helium elements present in the star. For example, the fraction of the Sun
Main_sequence
Central region of the Sun
primarily helium, which is the same composition as the atmosphere of Jupiter, and the primordial composition of gases at the earliest star formation after
Solar_core
Interaction between subatomic particles
electron and an electron antineutrino. Weak interaction is important in the fusion of hydrogen into helium in a star. This is because it can convert a proton
Weak_interaction
Star in the constellation Andromeda
silicon abundance, but has been reported to actually be a helium-weak chemically peculiar star. The star has just over three times the mass of the Sun and about
KK_Andromedae
Class of young variable stars
calculate the age of the star. Several types of TTSs exist: Classical T Tauri star (CTTS) Weak-line T Tauri star (WTTS) Naked T Tauri star (NTTS), which is a
T_Tauri_star
Hypothetical early-universe star with a black hole core
before hydrogen and helium were contaminated by heavier elements; thus, they may have been very massive Population III stars. A quasi-star would have resulted
Quasi-star
Star in the constellation Lynx
with a heliocentric radial velocity of 21 km/s. This is a magnetic, helium-weak Bp star with a stellar classification of B9IVpHgMn, although the spectral
36_Lyncis
Star in the constellation of Lupus
magnetic B star, showing an averaged quadratic field strength of (167.2±140.4)×10−3 T. Helium-weak, it displays an underabundance of helium in its spectrum
HD_143699
Stage of stellar evolution
contributes more helium. If the star has more than about 0.5 solar masses, the core eventually reaches the temperature necessary for the fusion of helium into carbon
Horizontal_branch
Type of cool giant star
intermediate with carbon stars, have weak or undetectable ZrO, but strong sodium D lines and detectable but weak C2 bands. S star spectra also show other differences
S-type_star
Type of variable star
"Radial velocities for the hydrogen-deficient star HD 168476, several helium-strong and helium-weak stars". Astronomy and Astrophysics Supplement Series
PV_Telescopii_variable
Visible star that is nearly aligned with Earth's axis of rotation
A pole star is a visible star that is approximately aligned with the axis of rotation of an astronomical body; that is, a star whose apparent position
Pole_star
Dim, low mass stars on the main sequence
convective. Hence, the helium produced by the thermonuclear fusion of hydrogen is constantly remixed throughout the star, avoiding helium buildup at the core
Red_dwarf
Type of star that is massive and luminous
dredge-ups during shell burning, or by the loss of the outer layers of the star. Helium is formed in the core and shell by fusion of hydrogen and nitrogen, which
Supergiant
Explosion of a star 8 to 45 times the mass of the Sun
the star from collapsing, maintaining stellar equilibrium. The star fuses increasingly higher mass elements, starting with hydrogen and then helium, progressing
Type_II_supernova
Triple star system in the constellation Centaurus
chemically peculiar star of the helium-weak (CP4) variety, and has a stellar classification of B5 III-IVp. The spectrum of the star displays overabundances
3_Centauri
Isolated, small, and opaque nebula
oxides and helium, and around 1% (by mass) silicate dust. Bok globules most commonly result in the formation of double- or multiple-star systems. Bok
Bok_globule
Nuclear fusion reaction
product of the previous reaction and helium. The later-stage reactions which are able to begin in any particular star, do so while the prior stage reactions
Alpha_process
Hot, giant star of early spectral type
burning helium in their cores. Depending on mass and chemical composition these stars gradually move bluewards until they exhaust the helium in their
Blue_giant
Small number of stars that orbit each other
single star. A large group of stars bound by gravitation is generally called a star cluster or galaxy, although, broadly speaking, they are also star systems
Star_system
Grouping of stars by similar metallicity
In astrophysics nomenclature metal refers to all elements heavier than helium, including chemical non-metals such as oxygen. By definition, each population
Stellar_population
Clustering of stars in astronomy diagram
stars originally similar to the Sun which have undergone a helium flash and are now fusing helium in their cores. Red clump stellar properties vary depending
Red_clump
Type of star
lines are very common, but may be weak or absent in cooler stars; FeII lines are common but not always present; helium lines may be seen in the hottest
Shell_star
Fluid which flows without losing kinetic energy
linked: at low temperature, liquid helium has a large superfluid fraction but a low condensate fraction; while a weakly interacting BEC, with almost unity
Superfluidity
Stars with a supergiant luminosity class with a spectral type of K or M
completely consumed. In the latest stages of mass loss, before a star explodes, surface helium may become enriched to levels comparable with hydrogen. In theoretical
Red_supergiant
Planetary nebula
(FLIER). The central star of M2-42 is classified as weak emission-line star, but its nitrogen and helium features may be linked to nitrogen sequences of Wolf-Rayet
M2-42
Hypothetical types of stars
proportion of helium-4 nuclei, which are bosons, and smaller amounts of various heavier nuclei, which can be either. For this type of star to exist, there
Exotic_star
Stage in the evolution of some stars
occurs after a star enters the asymptotic giant branch, after a flash occurs in a helium-burning shell. The third dredge-up brings helium, carbon, and the
Dredge-up
Early stage in the process of star formation
a pre-main-sequence star, which contracts to later become a main-sequence star at the onset of hydrogen fusion producing helium. The modern picture of
Protostar
Scatter plot of stars showing the relationship of luminosity to stellar classification
nuclear fusion and correctly proposed that the star's source of power was the combination of hydrogen into helium, liberating enormous energy. This was a particularly
Hertzsprung–Russell_diagram
Subdwarf star with spectral type O
star is believed to be a carbon and oxygen core surrounded by a helium burning shell. The spectrum shows that the content is from 50 to 100% helium.
Subdwarf_O_star
Star in the constellation Canis Major
cooler, and less luminous B-type main sequence star. It is also a chemically peculiar helium-weak star. In 1977, Mikolaj Jerzykiewicz and Christiaan Sterken
HR_2501
Star of relatively small size and low luminosity
dwarf is a substellar object not massive enough to ever fuse hydrogen into helium, but still massive enough to fuse deuterium – less than about 0.08 M☉ and
Dwarf_star
Spectroscopic binary star system in the constellation Puppis
The Wolf-Rayet star shows no hydrogen in its spectrum and is thought to be hydrogen-free. It is calculated to consist of 42% helium and 58% heavier elements
WR_9
Gravitational process studied in astronomy
particles per cm3, and is typically composed of roughly 70% hydrogen, 28% helium, and 1.5% heavier elements by mass. The trace amounts of heavier elements
Star_formation
Region at the center of a star
through thermonuclear fusion of hydrogen into helium. This energy in turn counterbalances the mass of the star pressing inward; a process that self-maintains
Stellar_core
Euthanasia device using inert gas
with a flow of an inert gas that is lighter or less dense than air, like helium or nitrogen. Continuing to breathe expels carbon dioxide and this prevents
Suicide_bag
Hypothetical astronomical object
loop quantum gravity theory, a Planck star is a hypothetical astronomical object, theorized as a compact, exotic star, that exists within a black hole's
Planck_star
Star in the Triangulum Galaxy
lines of hydrogen and atomic helium, along with a broad complex of ionised nitrogen emission lines and weak ionised helium emission. There are also some
Romano's_Star
Visual binary star system in the constellation of Lupus
main-sequence star. Hiltner et al. (1969) gave a class of B3 IVp, which is still used in some studies. It is a helium-weak chemically peculiar star showing
KT_Lupi
Collapsed core of a massive star
for those that are especially rich in elements heavier than hydrogen and helium. There are thought to be around one billion neutron stars in the Milky Way
Neutron_star
Star in the constellation of Scorpius
main-sequence star with a spectral type of B6Vp and a mass estimated at 3.7 times the solar mass. HIP 77900 is a helium-weak chemically peculiar star, and has
HD_142250
Star in the constellation Centaurus
the stellar surface. In particular, HD 105382 is a helium-weak chemically peculiar star with a helium abundance varying between 0.5% and 15% of the solar
HD_105382
Star that has a supergiant luminosity class, with a spectral type of F or G
confirmed then an explanation must be found for how a star of moderate mass still with a helium core would cause a core-collapse supernova. The obvious
Yellow_supergiant
Theoretical stellar remnant
processes occur, preventing any supernova explosions. Once the Sun stops fusing helium in its core and ejects its layers in a planetary nebula in about 8 billion
Black_dwarf
Star in the constellation Cygnus
departures from solar element abundances. A moderate helium deficiency is observed in the star. The relative abundance log(He/H) is approximately −1
HD_188101
Variable star in the constellation Canis Major
main-sequence star.) It is a magnetic Bp star of the helium–weak variety (CP4), with the spectrum displaying evidence for vertical stratification of helium in the
12_Canis_Majoris
Star in the constellation Puppis
main-sequence star with a stellar classification of B2V. It is a magnetic chemically peculiar star of the helium strong variety with weak hydrogen alpha
HD_64740
Star in the constellation Telescopium
"Radial velocities for the hydrogen-deficient star HD 168476, several helium-strong and helium-weak stars". Astronomy and Astrophysics Supplement Series
PV_Telescopii
Star whose brightness fluctuates, as seen from Earth
spectra are peculiar by having weak hydrogen but extra strong carbon and helium lines, making this a type of extreme helium star. The prototype for this category
Variable_star
Astrophysical limit on radiation from stars
it is for hydrogen. In an evolved star with a pure helium atmosphere, the electric field would have to lift a helium nucleus (an alpha particle), with
Eddington_luminosity
Object with escape velocity exceeding the speed of light
identify the surface gravity of a distant star by seeing how far the star's light was shifted to the weaker end of the spectrum, a precursor of Einstein's
Dark star (Newtonian mechanics)
Dark_star_(Newtonian_mechanics)
Star of luminosity class VI under the Yerkes spectral classification system
helium. The lower metallicity decreases the opacity of their outer layers and decreases the radiation pressure, resulting in a smaller, hotter star for
Subdwarf
Supernova that ejects a large mass at unusually high velocity
carbon-oxygen star lacking any significant hydrogen or helium, of Type Ic supernovae was once thought to be an extremely evolved massive star, for example
Hypernova
Star not gravitationally bound to any galaxy
measure of the proportion of chemical elements other than hydrogen and helium within a star) indicating an inner galactic origin, since stars outside the disks
Intergalactic_star
Stage of stellar evolution
lifetime of a star. Stars on the asymptotic giant branch (AGB) have largely inert cores of carbon and oxygen, and alternately fuse hydrogen and helium in concentric
Blue_loop
Nuclear fusion reaction
reactions within the star, and diprotons almost immediately decay back into two protons. Since the conversion of hydrogen to helium is slow, the complete
Proton–proton_chain
Bookkeeping survey of stars
Star counts are census counts of stars and the statistical and geometrical methods used to correct the corresponding data for bias.[citation needed] The
Star_count
Star in the constellation Gemini
km·s−1. The abundance of elements other than hydrogen and helium, what astronomers term the star's metallicity, is uncertain, with estimates ranging from
Pollux_(star)
Region of a star
solar masses, the outer envelope of the star contains a region where partial ionization of hydrogen and helium raises the heat capacity. The relatively
Convection_zone
Star in the constellation Scorpius
HD 144941 is a massive helium-strong star in the southern constellation of Scorpius. With an apparent visual magnitude of 10.1, it requires a telescope
HD_144941
Type of star larger than main-sequence but smaller than a giant
fuse hydrogen in their cores until essentially the entire star has been converted to helium, and they do not develop into subgiants. Stars of this mass
Subgiant
Astrophysical phenomenon
occur when material is accreted from a helium-rich companion rather than a hydrogen-rich star. Because of helium lines in their spectra, they can resemble
Supernova
Gas and dust surrounding a newly formed star
of dense gas and dust surrounding a young newly formed star, a T Tauri star, or Herbig Ae/Be star. The protoplanetary disk may not be considered an accretion
Protoplanetary_disk
Portion of the giant branch before helium ignition
called the first giant branch, is the portion of the giant branch before helium ignition occurs in the course of stellar evolution. It is a stage that follows
Red-giant_branch
Process of nucleosynthesis
hydrogen are also rich in helium. The time scale for the rp-process is set by β+ decays at or near the proton drip line, because the weak interaction is notoriously
Rp-process
Type of celestial body
burn hydrogen in an inner shell. Members of this class of stars switch to helium shell burning with an interval of some 100,000 years, in "dredge-ups". Technetium
Technetium_star
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HELIUM WEAK-STAR
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HELIUM WEAK-STAR
HELIUM WEAK-STAR
HELIUM WEAK-STAR
HELIUM WEAK-STAR
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